Vacuum pumps for refrigeration system servicing must be portable and readily transportable by service personnel. Such vacuum pumps basically conist of an electric motor having pump apparatus attached to one end of the motor and driven thereby, and refrigeration servicing vacuum pumps are usually of the single or double stage type, typical examples being shown in the assignee's U.S. Pat. Nos. 3,791,780; 3,837,764 and 3,982,864.
The vacuum producing capabilities of refrigeration servicing pumps may vary in accord with the system being evacuated, and in many service calls for domestic refrigerators, home air conditioning units, such as window units, and other relatively small refrigeration systems, a vacuum pump of relatively limited capacity is most suitable. While many refrigeration systems could be serviced by relatively small capacity vacuum pumps, because of marketing and pricing factors, smaller capacity vacuum pumps have not been available wherein excellent vacuum achieving capabilities have been combined with concise configuration and low cost.
It is an object of the invention to provide a lightweight and concise vacuum pump which is readily transportable and easy to use.
Another object of the invention is to provide a concise vacuum pump utilizing a motor casing wherein a dielectric handle assembly is mounted on the casing incorporating the motor capacitor.
A further object of the invention is to provide a concise vacuum pump including an adapter and pump assembly shell wherein the configuration of these components is substantially cylindrical and of a diameter substantially corresponding to that of the motor casing.
An additional object of the invention is to provide a concise vacuum pump having a pump rotor directly mounted upon the electric motor armature shaft, and wherein passages are provided for improving lubrication of the pump to insure an effective extended operating life.
Yet another object of the invention is to provide a concise vacuum pump having a pump assembly employing an exhaust riser protecting a reed valve, and utilizing a vapor discharge which aids in separating exhausted gas and vapors from oil.
In the practice of the invention a cylindrical electric motor casing is closed at one end with a conventional end plate, and a cylindrical adapter encloses the other casing end. Tie rods maintain the end plate and adapter in position, and the motor armature shaft is rotatably mounted upon bearings located on the end plate and adapter.
The adapter includes a pump assembly mounting base defined thereon to which is bolted a pump assembly including a rotor eccentrically oriented within a cylindrical cavity and the rotor employs outwardly biased vanes engaging the cavity circumference to form a vane-type pump. A hollow shell encompasses the pump assembly defining a chamber thereabout, and forming a sump for the lubricating oil as well as a space for receiving the gases exhausted from the pump wherein separation of exhausted gas and lubricating oil vapor and droplets takes place.
A synthetic plastic housing assembly is directly mounted upon the motor casing and includes a portion enclosing the motor capacitor, and a handle portion extends thereabove to permit ease of carrying of the pump. An electric switch is mounted upon the handle assembly at the end of the capacitor housing portion.
A base assembly including elastic foot pads is attached to the lower region of the motor casing upon which the unit rests.
The motor armature shaft extends through the adapter and the pump rotor is directly mounted thereon. Other features of the pump include the use of a spacer metering washer having a lubricating oil passage defined therein whereby lubricating oil is drawn at a metered rate from the sump into the pump assembly, and the pump assembly includes an end plate having a passage in communication with the metering washer or spacer for distributing oil to the pump cavity. The adapter mounting base also includes a lubricating passage communicating with the sump.
Another feature of the pump is the utilization of an exhaust riser which is attached to the pump assembly and is vertically oriented for housing the reed valve and reed valve limiter associated with the pump exhaust orifice. A distribution conduit affixed to the upper region of the exhaust riser communicating with the shell chamber and extending through the baffle screen aids in separating gas and oil particles. The exhaust orifice, at the pump cavity surface, is relieved to define a packet to produce an increased volume and dimension at the exhaust port which increases the effective pressure on the exhaust reed valve causing the valve to open earlier in the cycle than would otherwise occur which improves the vacuum attainable.